U.S. Pat. No. 2,805,214 discloses the ring opening polymerization of .epsilon.-caprolactam with the use of a strong ionic base catalyst comprising an alkali metal hydroxide together with an alkali metal, alkali metal amide or alkali metal hydride.
U.S. Pat. No. 3,236,817 discloses the ring opening polymerization of .epsilon.-caprolactam with the use of strong ionic base catalysts comprising an alkali metal or alkali metal hydride and alkaline earth metals or alkaline earth metal hydrides.
J-S. Tang and J. G. Verkade, Angew., Chem. Int. Ed. Engl., 32, 896 (1993) disclose the use of phosphazene bases in the conversion of isocyanates to isocyanurates.
T. Pietzonka and D. Seebach, Angew., Chem. Int. Ed. Engl., 32, 716 (1993) report the use of P.sub.4 -phosphazene base as a metal free initiator system for the anionic polymerization of methyl methacrylate.